ASTM D7615/D7615M-23

Standard Practice for Open-Hole Fatigue Response of Polymer Matrix Composite Laminates

SIGNIFICANCE AND USE
5.1 Refer to Guide D8509.
SCOPE
1.1 This practice provides instructions for modifying static open-hole tensile and compressive strength test methods to determine the fatigue behavior of composite materials subjected to cyclic tensile or compressive forces, or both. The composite material forms are limited to continuous-fiber reinforced polymer matrix composites in which the laminate is both symmetric and balanced with respect to the test direction. The range of acceptable test laminates and thicknesses are described in 8.2.  
1.2 This practice supplements Test Methods D5766/D5766M and D6484/D6484M with provisions for testing specimens under cyclic loading. Several important test specimen parameters, for example fatigue force (stress) ratio, are not mandated by this practice; however, repeatable results require that these parameters be specified and reported.  
1.3 This practice is limited to test specimens subjected to constant amplitude uniaxial loading, where the machine is controlled so that the test specimen is subjected to repetitive constant amplitude force (stress) cycles. Either engineering stress or applied force may be used as a constant amplitude fatigue variable. The repetitive loadings may be tensile, compressive, or reversed, depending upon the test specimen and procedure utilized.  
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.4.1 Within the text the inch-pound units are shown in brackets.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Aug-2023
• ICS: 83.120 - Reinforced plastics
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.05 - Structural Test Methods

Relations

• Replaces: ASTM D7615/D7615M-19 - Standard Practice for Open-Hole Fatigue Response of Polymer Matrix Composite Laminates
• Effective Date: 01-Sep-2023
• Refers: ASTM E1823-24a - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 15-Feb-2024
• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM E1823-24 - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM E1823-23 - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 01-Feb-2023
• Refers: ASTM E739-23 - Standard Guide for Statistical Analysis of Linear or Linearized Stress-Life (<emph type="bdit">S-N</emph>) and Strain-Life (ε-<emph type="bdit" >N</emph>) Fatigue Data (Withdrawn 2024)
• Effective Date: 01-Feb-2023
• Refers: ASTM D883-22 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2022
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E456-13a(2022) - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM D6484/D6484M-20 - Standard Test Method for Open-Hole Compressive Strength of Polymer Matrix Composite Laminates
• Effective Date: 01-Oct-2020
• Referred By: ASTM D4762-23 - Standard Guide for Testing Polymer Matrix Composite Materials
• Effective Date: 01-Sep-2023
• Referred By: ASTM D8509/D8509M-23 - Standard Guide for Test Method Selection and Test Specimen Design for Bolted Joint Related Properties
• Effective Date: 01-Sep-2023
• Referred By: ASTM D6484/D6484M-23 - Standard Test Method for Open-Hole Compressive Strength of Polymer Matrix Composite Laminates
• Effective Date: 01-Sep-2023

Overview

ASTM D7615/D7615M-23 is the international standard practice developed by ASTM International for evaluating the open-hole fatigue response of polymer matrix composite laminates. This standard defines procedures for modifying static strength test methods to assess the fatigue behavior of continuous-fiber reinforced composite materials with symmetric and balanced laminate configurations. The standard focuses on the response of these composites when subjected to cyclic tensile, compressive, or both types of uniaxial loading under constant amplitude conditions.

Composites tested under this practice are primarily used in critical structural applications where durability and resistance to fatigue-induced damage-such as microscopic cracking, fiber fracture, or delamination-are essential for safety and reliability. Following the methods outlined ensures accurate and repeatable measurement of fatigue life and related properties for design, quality assurance, and research.

Key Topics

• Scope of Application: Applies to continuous-fiber reinforced polymer matrix composite laminates with symmetric and balanced layups relative to the loading direction.
• Fatigue Testing Protocol: Supplements existing static open-hole tensile (ASTM D5766/D5766M) and compressive (ASTM D6484/D6484M) test methods to include cyclic loading.
• Test Specimens: Focuses on specimens under constant amplitude uniaxial loading, which may be tensile, compressive, or reversed, with machine control to ensure consistent loading cycles.
• Parameters to Report: Test results are influenced by variables such as material, laminate stacking sequence, specimen geometry, loading frequency, environment, specimen alignment and gripping, and moisture conditioning. Documenting such factors is critical for data integrity.
• Data Outputs: Key deliverables include fatigue life at specified conditions, stiffness degradation versus cycles, and residual strengths after fatigue exposure. Such data support S-N curve development for design and reliability evaluation.
• Statistical Guidance: Recommends use of appropriate sample sizes and statistical methods, such as log-normal and Weibull distributions, to analyze fatigue life data and ensure robust conclusions.

Applications

• Material Specification and Qualification: Supports material selection and certification for aerospace, automotive, marine, and civil engineering applications where polymer matrix composites are exposed to cyclic stresses.
• Design Allowables: Provides essential test data for the development of design allowables, enabling engineers to predict long-term performance and safety margins for composite components incorporating open holes (such as fastener locations).
• Quality Assurance: Ensures consistent evaluation of production batches by applicable test specimen preparation, conditioning, and documentation procedures, minimizing risks caused by material or manufacturing variability.
• Research and Development: Facilitates advanced materials research by giving structured, reproducible methods for characterizing fatigue performance in new composite systems or layup configurations.
• Failure Analysis: Helps engineers study fatigue damage mechanisms like delamination or crack initiation and propagation in the vicinity of notches or holes, guiding improvements in composite laminate design for increased durability.

Related Standards

• ASTM D5766/D5766M - Open-Hole Tensile Strength of Polymer Matrix Composite Laminates
• ASTM D6484/D6484M - Open-Hole Compressive Strength of Polymer Matrix Composite Laminates
• ASTM D8509 - Guide for Test Method Selection and Specimen Design for Bolted Joint Related Properties
• ASTM D5229/D5229M - Test Method for Moisture Absorption of Polymer Matrix Composite Materials
• ASTM E739 - Guide for Statistical Analysis of Fatigue Data
• ASTM E467 - Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing System

By adhering to ASTM D7615/D7615M-23, laboratories and engineers ensure consistent, reliable assessment of open-hole fatigue response in polymer matrix composite laminates, enabling safer, high-performance composite structures across industries.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7615/D7615M − 23
Standard Practice for
Open-Hole Fatigue Response of Polymer Matrix Composite
Laminates
This standard is issued under the fixed designation D7615/D7615M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This practice provides instructions for modifying static
1.6 This international standard was developed in accor-
open-hole tensile and compressive strength test methods to
dance with internationally recognized principles on standard-
determine the fatigue behavior of composite materials sub-
ization established in the Decision on Principles for the
jected to cyclic tensile or compressive forces, or both. The
Development of International Standards, Guides and Recom-
composite material forms are limited to continuous-fiber rein-
mendations issued by the World Trade Organization Technical
forced polymer matrix composites in which the laminate is
Barriers to Trade (TBT) Committee.
both symmetric and balanced with respect to the test direction.
The range of acceptable test laminates and thicknesses are
2. Referenced Documents
described in 8.2.
2.1 ASTM Standards:
1.2 This practice supplements Test Methods D5766/
D883 Terminology Relating to Plastics
D5766M and D6484/D6484M with provisions for testing
D3878 Terminology for Composite Materials
specimens under cyclic loading. Several important test speci-
D5229/D5229M Test Method for Moisture Absorption Prop-
men parameters, for example fatigue force (stress) ratio, are not
erties and Equilibrium Conditioning of Polymer Matrix
mandated by this practice; however, repeatable results require
Composite Materials
that these parameters be specified and reported.
D5766/D5766M Test Method for Open-Hole Tensile
1.3 This practice is limited to test specimens subjected to Strength of Polymer Matrix Composite Laminates
constant amplitude uniaxial loading, where the machine is
D6484/D6484M Test Method for Open-Hole Compressive
controlled so that the test specimen is subjected to repetitive Strength of Polymer Matrix Composite Laminates
constant amplitude force (stress) cycles. Either engineering
D8509 Guide for Test Method Selection and Test Specimen
stress or applied force may be used as a constant amplitude
Design for Bolted Joint Related Properties
fatigue variable. The repetitive loadings may be tensile, E4 Practices for Force Calibration and Verification of Test-
compressive, or reversed, depending upon the test specimen
ing Machines
and procedure utilized. E6 Terminology Relating to Methods of Mechanical Testing
E83 Practice for Verification and Classification of Exten-
1.4 The values stated in either SI units or inch-pound units
someter Systems
are to be regarded separately as standard. The values stated in
E122 Practice for Calculating Sample Size to Estimate, With
each system are not necessarily exact equivalents; therefore, to
Specified Precision, the Average for a Characteristic of a
ensure conformance with the standard, each system shall be
Lot or Process
used independently of the other, and values from the two
E177 Practice for Use of the Terms Precision and Bias in
systems shall not be combined.
ASTM Test Methods
1.4.1 Within the text the inch-pound units are shown in
E456 Terminology Relating to Quality and Statistics
brackets.
E467 Practice for Verification of Constant Amplitude Dy-
1.5 This standard does not purport to address all of the
namic Forces in an Axial Fatigue Testing System
safety concerns, if any, associated with its use. It is the
E739 Guide for Statistical Analysis of Linear or Linearized
responsibility of the user of this standard to establish appro-
Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
E1823 Terminology Relating to Fatigue and Fracture Testing
This practice is under the jurisdiction of ASTM Committee D30 on Composite
Materials and is the direct responsibility of Subcommittee D30.05 on Structural Test
Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Sept. 1, 2023. Published September 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2011. Last previous edition approved in 2019 as D7615/D7615M – 19. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D7615_D7615M-23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7615/D7615M − 23
3. Terminology tion curve obtained by quasi-statically loading the specimen
through one tension, compression, or tension-compression
3.1 Definitions—Terminology D3878 defines terms relating
cycle as applicable. Determine the number of force cycles at
to high-modulus fibers and their composites. Terminology
which failure occurs (or at which a predetermined change in
D883 defines terms relating to plastics. Terminology E6 defines
specimen stiffness is observed) for a specimen subjected to a
terms relating to mechanical testing. Terminology E1823
specific force (stress) ratio and stress magnitude. Refer to
defines terms relating to fatigue. Terminology E456 and
Guide D8509 for additional test details.
Practice E177 define terms relating to statistics. In the event of
a conflict between terms, Terminology D3878 shall have
5. Significance and Use
precedence over the other standards.
5.1 Refer to Guide D8509.
NOTE 1—If the term represents a physical quantity, its analytical
dimensions are stated immediately following the term (or letter symbol) in
6. Interferences
fundamental dimension form, using the following ASTM standard sym-
bology for fundamental dimensions, shown within square brackets: [M]
6.1 Refer to Guide D8509.
for mass, [L] for length, [T] for time, [θ] for thermodynamic temperature,
and [nd] for non-dimensional quantities. Use of these symbols is restricted
7. Apparatus
to analytical dimensions when used with square brackets, as the symbols
7.1 General Apparatus—General apparatus shall be in ac-
may have other definitions when used without the brackets.
cordance with Test Method D5766/D5766M Configuration A
3.2 Definitions of Terms Specific to This Standard—Refer to
for tension-tension fatigue loading, and in accordance with Test
Guide D8509.
Method D6484/D6484M Procedure A for tension-compression
3.3 Symbols:
and compression-compression fatigue loading. The micrometer
or gauge used shall be capable of determining the hole
A = Cross-sectional area of a specimen
diameter to 60.025 mm [60.001 in.].
D = specimen hole diameter
h = specimen thickness
7.2 Testing Machine—In addition to the requirements de-
K = specimen chord stiffness, P/δ
scribed in Test Methods D5766/D5766M or D6484/D6484M,
K = specimen chord stiffness prior to fatigue cycles
i the testing machine shall be in conformance with Practice E467
K = specimen chord stiffness after N fatigue cycles
N
and shall satisfy the following requirements:
N = number of constant amplitude cycles
7.2.1 Drive Mechanism and Controller—The velocity of the
Δ = change in chord stiffness after N fatigue cycles
N
movable head shall be capable of being regulated under cyclic
P = force carried by specimen
force (stress) conditions. The drive mechanism and controller
maxq
P = peak force under quasi-static loading for measure-
shall be capable of imparting a continuous loading wave form
ment of stiffness
minq to the specimen. It is important to minimize drift of the fatigue
P = valley force under quasi-static loading for measure-
loading away from the maximum and minimum values.
ment of stiffness
Achieving such accuracy is critical in the development of
w = specimen width
reliable fatigue life data since small errors in loading may
δ = crosshead or extensometer translation
alt
result in significant errors in fatigue life. It is recommended
σ = alternating open hole stress during fatigue loading
max
that the test controller be equipped with a Test Amplitude
σ = value of stress corresponding to the peak value of
controller, capable of monitoring the fatigue forces at least
force (stress) under constant amplitude loading
maxq
σ = value of stress corresponding to the peak value of once every three cycles.
7.2.2 Force Indicator—The force indicator shall be in com-
force (stress) under quasi-static loading for measure-
ment of stiffness, given by the greater of the pliance with Practices E4. The fatigue rating of the force
max min
indicator shall exceed the forces at which testing will take
absolute values of σ and 0.5 × σ
mean
σ = mean normal stress during fatigue loading place. Additionally, this practice recommends compliance with
min
σ = value of stress corresponding to the valley value of
Practice E467 for the development of a system dynamic
force (stress) under constant amplitude loading
conversion for the verification of specimen forces to within
minq
σ = value of stress corresponding to the valley value of
1 % of true forces.
force (stress) under quasi-static loading for measure-
7.2.3 Extensometers—The extensometer gauge length shall
ment of stiffness, given by the greater of the
be 25 mm [1.0 in.]. Extensometers shall satisfy, at a minimum,
min max
absolute values of σ and 0.5 × σ
Practice E83, Class B-1 requirements for the strain range of
ohm
σ = maximum cyclic open hole stress magnitude, given
interest, and shall be calibrated over that range in accordance
max min
by the greater of the absolute values of σ and σ
with Practice E83. The extensometers shall be essentially free
of intertia lag at the specified speed of testing.
4. Summary of Practice
7.2.4 Grips—As described in Test Method D5766/D5766M
4.1 In accordance with Test Methods D5766/D5766M or for tension-tension fatigue loading or Test Method D6484/
D6484/D6484M, but under constant amplitude fatigue loading, D6484M Procedure A for tension-compression and
perform a uniaxial test of an open-hole specimen. Cycle the compression-compression fatigue loading, where use of hy-
specimen between minimum and maximum axial forces draulic grips is recommended for fatigue loading. The grips
(stresses) at a specified frequency. At selected cyclic intervals, shall have sufficient fatigue rating for forces at which testing
determine the specimen stiffness from a force versus deforma- will take place.
D7615/D7615M − 23
7.3 Support Fixture—If compressive forces are applied, does not explicitly specify a pre-test conditioning environment,
either during fatigue loading or during quasi-static loading to no conditioning is required and the test specimens may be
determine residual strength or monitor specimen stiffness, a tested as prepared.
support fixture shall be used to stabilize the specimen. The
10.2 The pre-test specimen conditioning process, to include
support fixture shall be in accordance with that described in
specified environmental exposure levels and resulting moisture
Test Method D6484/D6484M.
content, shall be reported with the test data.
NOTE 2—The term moisture, as used in Test Method D5229/D5229M,
7.4 Thermocouple and Temperature Recording Devices,
includes not only the vapor of a liquid and its condensate, but the liquid
capable of reading specimen temperature to 60.5 °C
itself in large quantities, as for immersion.
[61.0 °F].
10.3 If no explicit conditioning process is performed, the
8. Sampling and Test Specimens specimen conditioning process shall be reported as “uncondi-
tioned” and the moisture content as “unknown.”
8.1 Sampling—For statistically significant data, the proce-
dures outlined in Practice E122 should be consulted. From the 10.4 Maintaining testing environment is critical to obtaining
consistent fatigue data since testing for long periods of time
number of tests selected a statistically significant distribution
of data should be obtained for a given material, stacking (days or weeks) is not uncommon. For unattended tests, the test
environment shall be monitored so that unintended changes in
sequence, environment, and loading condition.
8.1.1 Sample Size for S-N Curve—The recommended mini- the test environment result in suspension of the test. Report the
mum number of specimens in the development of S-N data is testing environment for the duration of the test.
described in Table 1. A minimum of three different force
11. Procedure
(stress) levels is recommended in development of S-N data.
For additional procedures consult Practice E739.
11.1 Parameters to Be Specified Prior to Test:
11.1.1 The specimen sampling method, specimen type and
8.2 Geometry—In addition to the requirements described in
min
geometry, minimum and maximum test forces (stresses) σ
Test Methods D5766/D5766M and D6484/D6484M, the speci-
max
and σ for each test, force (stress) ratio for each test, test
men geometry shall satisfy the following requirements:
frequency and wave form of the fatigue loading. For the
8.2.1 Stacking Sequence—The stacking sequence should be
purpose of development of an S-N curve, all specimens shall
evaluated for free edge effects to minimize the likelihood of
be tested at the same frequency and wave form unless that is a
edge delamination initiation.
factor to be studied in the test.
8.2.2 Specimen Configuration—The test specimen configu-
11.1.2 Fatigue cycle counts at which stiffness is to be
ration shall be in accordance with Test Methods D5766/
measured, method of measuring stiffness, quasi-static peak and
D5766M Configuration A for tension-tension loading or
valley forces for stiffness measurement (if applicable), stiffness
D6484/D6484M for tension-compression and compression-
level at which fatigue loading shall cease, and run-out cycles.
compression loading.
NOTE 3—Fatigue damage accumulation curves are “S” shaped requiring
8.3 Specimen Preparation—Specimens shall be prepared in
more data points at earlier cycles and again closer to failure (the latter
accordance with Test Method D5766/D5766M or Test Method
requires some estimate of N at failure) to capture the damage accumula-
D6484/D6484M. Special care should be taken to ensure that
tion behavior. For example, during a 2 million cycle test, stiffness may be
specimen edges are sufficiently free of obvious flaws as
checked at the following intervals: N = 1, 2, 5, 10, 20, 50, 100, 200, 500,
determined by visual inspection. Such flaws may lead to
1000, 2000, 5000, 10 000, 20 000, 50 000, and every 100 000 cycles
thereafter. The final interval is typically constant and should be one order
premature failure due to edge delamination.
of magnitude less than the anticipated N at failure.
9. Calibration
11.1.3 All other parameters documented in Test Methods
D5766/D5766M or D6484/D6484M.
9.1 The accuracy of all measuring equipment shall have
certified calibrations that are current at the time of use of the
11.2 General Instructions:
equipment.
11.2.1 Any deviations from these procedures, whether in-
tentional or inadvertent, shall be reported.
10. Conditioning
11.2.2 Perform general instructions for conditioning,
measurement, cleaning, and assembly in accordance with Test
10.1 The recommended pre-test condition is effective mois-
Methods D5766/D5766M or D6484/D6484M.
ture equilibrium at a specified relative humidity as establis
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7615/D7615M − 19 D7615/D7615M − 23
Standard Practice for
Open-Hole Fatigue Response of Polymer Matrix Composite
Laminates
This standard is issued under the fixed designation D7615/D7615M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice provides instructions for modifying static open-hole tensile and compressive strength test methods to determine
the fatigue behavior of composite materials subjected to cyclic tensile or compressive forces, or both. The composite material
forms are limited to continuous-fiber reinforced polymer matrix composites in which the laminate is both symmetric and balanced
with respect to the test direction. The range of acceptable test laminates and thicknesses are described in 8.2.
1.2 This practice supplements Test Methods D5766/D5766M and D6484/D6484M with provisions for testing specimens under
cyclic loading. Several important test specimen parameters, for example fatigue force (stress) ratio, are not mandated by this
practice; however, repeatable results require that these parameters be specified and reported.
1.3 This practice is limited to test specimens subjected to constant amplitude uniaxial loading, where the machine is controlled
so that the test specimen is subjected to repetitive constant amplitude force (stress) cycles. Either engineering stress or applied force
may be used as a constant amplitude fatigue variable. The repetitive loadings may be tensile, compressive, or reversed, depending
upon the test specimen and procedure utilized.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.
1.4.1 Within the text the inch-pound units are shown in brackets.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
This practice is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.05 on Structural Test
Methods.
Current edition approved April 1, 2019Sept. 1, 2023. Published May 2019September 2023. Originally approved in 2011. Last previous edition approved in 20182019 as
D7615/D7615M–11(2018).D7615/D7615M – 19. DOI: 10.1520/D7615_D7615M-19.10.1520/D7615_D7615M-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7615/D7615M − 23
D883 Terminology Relating to Plastics
D3878 Terminology for Composite Materials
D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite
Materials
D5766/D5766M Test Method for Open-Hole Tensile Strength of Polymer Matrix Composite Laminates
D6484/D6484M Test Method for Open-Hole Compressive Strength of Polymer Matrix Composite Laminates
D8509 Guide for Test Method Selection and Test Specimen Design for Bolted Joint Related Properties
E4 Practices for Force Calibration and Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E83 Practice for Verification and Classification of Extensometer Systems
E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or
Process
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
E467 Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing System
E739 Guide for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
E1823 Terminology Relating to Fatigue and Fracture Testing
3. Terminology
3.1 Definitions—Terminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology D883
defines terms relating to plastics. Terminology E6 defines terms relating to mechanical testing. Terminology E1823 defines terms
relating to fatigue. Terminology E456 and Practice E177 define terms relating to statistics. In the event of a conflict between terms,
Terminology D3878 shall have precedence over the other standards.
NOTE 1—If the term represents a physical quantity, its analytical dimensions are stated immediately following the term (or letter symbol) in fundamental
dimension form, using the following ASTM standard symbology for fundamental dimensions, shown within square brackets: [M] for mass, [L] for length,
[T] for time, [θ] for thermodynamic temperature, and [nd] for non-dimensional quantities. Use of these symbols is restricted to analytical dimensions when
used with square brackets, as the symbols may have other definitions when used without the brackets.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 constant amplitude loading, n—in fatigue, a loading in which all of the peak values of force (stress) are equal and all of the
valley values of force (stress) are equal.
3.2.2 fatigue loading transition, n—in the beginning of fatigue loading, the number of cycles before the force (stress) reaches the
desired peak and valley values.
3.2.3 force, P [MLT ], n—the total force carried by a test specimen.
3.2.4 force (stress) ratio, R [nd], n—in fatigue loading, the ratio of the minimum applied force (stress) to the maximum applied
force (stress).
3.2.5 frequency, f [T ], n—in fatigue loading, the number of force (stress) cycles completed in 1 s (Hz).
3.2.6 nominal value, n—a value, existing in name only, assigned to a measurable property for the purpose of convenient
designation. Tolerances may be applied to a nominal value to define an acceptable range for the property.
3.2.7 peak, n—in fatigue loading, the occurrence where the first derivative of the force (stress) versus time changes from positive
to negative sign; the point of maximum force (stress) in constant amplitude loading.
-1 -2
3.2.8 residual strength, [ML T ], n—the value of force (stress) required to cause failure of a specimen under quasi-static loading
conditions after the specimen is subjected to fatigue loading.
3.2.9 run-out, n—in fatigue, an upper limit on the number of force cycles to be applied.
D7615/D7615M − 23
3.2.10 spectrum loading, n—in fatigue, a loading in which the peak values of force (stress) are not equal or the valley values of
force (stress) are not equal (also known as variable amplitude loading or irregular loading).
3.2.11 valley, n—in fatigue loading, the occurrence where the first derivative of the force (stress) versus time changes from
negative to positive sign; the point of minimum force (stress) in constant amplitude loading.
3.2.12 wave form, n—the shape of the peak-to-peak variation of the force (stress) as a function of time.
3.2 Definitions of Terms Specific to This Standard—Refer to Guide D8509.
3.3 Symbols:
A = Cross-sectional area of a specimen
D = specimen hole diameter
h = specimen thickness
K = specimen chord stiffness, P/δ
K = specimen chord stiffness prior to fatigue cycles
i
K = specimen chord stiffness after N fatigue cycles
N
N = number of constant amplitude cycles
Δ = change in chord stiffness after N fatigue cycles
N
P = force carried by specimen
maxq
P = peak force under quasi-static loading for measurement of stiffness
minq
P = valley force under quasi-static loading for measurement of stiffness
w = specimen width
δ = crosshead or extensometer translation
alt
σ = alternating open hole stress during fatigue loading
max
σ = value of stress corresponding to the peak value of force (stress) under constant amplitude loading
maxq
σ = value of stress corresponding to the peak value of force (stress) under quasi-static loading for measurement of stiffness,
max min
given by the greater of the absolute values of σ and 0.5 × σ
mean
σ = mean normal stress during fatigue loading
min
σ = value of stress corresponding to the valley value of force (stress) under constant amplitude loading
minq
σ = value of stress corresponding to the valley value of force (stress) under quasi-static loading for measurement of stiffness,
min max
given by the greater of the absolute values of σ and 0.5 × σ
ohm max min
σ = maximum cyclic open hole stress magnitude, given by the greater of the absolute values of σ and σ
4. Summary of Practice
4.1 In accordance with Test Methods D5766/D5766M or D6484/D6484M, but under constant amplitude fatigue loading, perform
a uniaxial test of an open-hole specimen. Cycle the specimen between minimum and maximum axial forces (stresses) at a specified
frequency. At selected cyclic intervals, determine the specimen stiffness from a force versus deformation curve obtained by
quasi-statically loading the specimen through one tension, compression, or tension-compression cycle as applicable. Determine the
number of force cycles at which failure occurs (or at which a predetermined change in specimen stiffness is observed) for a
specimen subjected to a specific force (stress) ratio and stress magnitude. Refer to Guide D8509 for additional test details.
5. Significance and Use
5.1 This practice provides supplemental instructions for using Test Methods Refer D5766/D5766M or D6484/D6484Mto obtain
open-hole fatigue data for material specifications, research and development, material design allowables, and quality assurance.
The primary property that results is the fatigue life of the test specimen under a specific loading and environmental condition.
Replicate tests may be used to obtain a distribution of fatigue life for specific material types, laminate stacking sequences,
environments, and loading conditions. Guidance in statistical analysis of fatigue data, such as determination of linearized stress
life (S-N) curves, can be found in Practice Guide E739D8509.
5.2 This practice can be utilized in the study of fatigue damage in a polymer matrix composite open-hole specimen such as the
occurrence of microscopic cracks, fiber fractures, or delaminations. The change in strength associated with fatigue damage may
be determined by discontinuing cyclic loading to obtain the static strength using Test Methods D5766/D5766M or D6484/
D6484M.
D7615/D7615M − 23
NOTE 2—This practice may be used as a guide to conduct variable amplitude loading. This information can be useful in the understanding of fatigue
behavior of composite structures under spectrum loading conditions, but is not covered in this standard.
5.3 Factors that influence open-hole fatigue response and shall therefore be reported include the following: material, methods of
material fabrication, accuracy of lay-up, laminate stacking sequence and overall thickness, specimen geometry, specimen
preparation (especially of the hole), specimen conditioning, environment of testing, type of support fixture, specimen alignment
and gripping, test frequency, force (stress) ratio, normal stress magnitude, void content, and volume percent reinforcement.
Properties that result include the following:
5.3.1 Specimen stiffness versus fatigue life curves for selected normal stress values.
5.3.2 Normal stress versus specimen stiffness curves at selected cyclic intervals.
5.3.3 Normal stress versus fatigue life curves for selected stress ratio values.
6. Interferences
6.1 Force (Stress) Ratio—Results are affected by the force (stress) ratio under which the tests are conducted. Experience has
demonstrated that reversed (tension-compression) force ratios are critical for fatigue-induced damage in open hole specimens, with
fully reversed tension-compression (R = –1) being the most critical force ratio.
6.2 Loading Frequency—Results are affected by the loading frequency at which the test is conducted. High cyclic rates may induce
heating within the specimen that may cause variations in specimen temperature and properties of the composite as discussed in
11.3.2. The temperature of the specimen should be monitored, and the frequency should be kept low enough to avoid significant
temperature variations, unless that is a factor to be studied during the test. For example, loading frequencies up to 5 Hz have been
used successfully. Varying the cyclic frequency during the test is generally not recommended, as the response may be sensitive to
the frequency utilized and the resultant thermal history.
6.3 Environment—Results are affected by the environmental conditions under which the tests are conducted. Laminates tested in
various environments can exhibit significant differences in both strength and failure mode. Experience has demonstrated that
elevated temperature, humid environments are generally critical for open hole fatigue-induced damage. However, critical
environments must be assessed independently for each material system, stacking sequence, and loading condition tested.
6.4 Method of Stiffness Measurement—Results are affected by the method used to monitor specimen stiffness. Force versus
deformation data provide an indication of specimen stiffness change due to damage formation. However, the accuracy of such
measurements is affected by factors such as strain indicator accuracy, signal noise, gauge length and extensometer slippage,
extensometer placement/location, grip slippage, load frame stiffness (for crosshead deflection data), and so forth.
6.5 Hole Preparation—Results are affected by the hole preparation procedures.
6.1 Other—Additional sources of potential data scatter are documented in Test Methods Refer to Guide D5766/D5766MD8509
and D6484/D6484M.
7. Apparatus
7.1 General Apparatus—General apparatus shall be in accordance with Test Method D5766/D5766M Configuration A for
tension-tension fatigue loading, and in accordance with Test Method D6484/D6484M Procedure A for tension-compression and
compression-compression fatigue loading. The micrometer or gauge used shall be capable of determining the hole diameter to
60.025 mm [60.001 in.].
7.2 Testing Machine—In addition to the requirements described in Test Methods D5766/D5766M or D6484/D6484M, the testing
machine shall be in conformance with Practice E467 and shall satisfy the following requirements:
7.2.1 Drive Mechanism and Controller—The velocity of the movable head shall be capable of being regulated under cyclic force
(stress) conditions. The drive mechanism and controller shall be capable of imparting a continuous loading wave form to the
specimen. It is important to minimize drift of the fatigue loading away from the maximum and minimum values. Achieving such
D7615/D7615M − 23
accuracy is critical in the development of reliable fatigue life data since small errors in loading may result in significant errors in
fatigue life. It is recommended that the test controller be equipped with a Test Amplitude controller, capable of monitoring the
fatigue forces at least once every three cycles.
7.2.2 Force Indicator—The force indicator shall be in compliance with Practices E4. The fatigue rating of the force indicator shall
exceed the forces at which testing will take place. Additionally, this practice recommends compliance with Practice E467 for the
development of a system dynamic conversion for the verification of specimen forces to within 1 % of true forces.
7.2.3 Extensometers—The extensometer gauge length shall be 25 mm [1.0 in.]. Extensometers shall satisfy, at a minimum, Practice
E83, Class B-1 requirements for the strain range of interest, and shall be calibrated over that range in accordance with Practice
E83. The extensometers shall be essentially free of intertia lag at the specified speed of testing.
7.2.4 Grips—As described in Test Method D5766/D5766M for tension-tension fatigue loading or Test Method D6484/D6484M
Procedure A for tension-compression and compression-compression fatigue loading, where use of hydraulic grips is recommended
for fatigue loading. The grips shall have sufficient fatigue rating for forces at which testing will take place.
7.3 Support Fixture—If compressive forces are applied, either during fatigue loading or during quasi-static loading to determine
residual strength or monitor specimen stiffness, a support fixture shall be used to stabilize the specimen. The support fixture shall
be in accordance with that described in Test Method D6484/D6484M.
7.4 Thermocouple and Temperature Recording Devices, capable of reading specimen temperature to 60.5 °C [61.0 °F].
8. Sampling and Test Specimens
8.1 Sampling—For statistically significant data, the procedures outlined in Practice E122 should be consulted. From the number
of tests selected a statistically significant distribution of data should be obtained for a given material, stacking sequence,
environment, and loading condition.
8.1.1 Sample Size for S-N Curve—The recommended minimum number of specimens in the development of S-N data is described
in Table 1. A minimum of three different force (stress) levels is recommended in development of S-N data. For additional
procedures consult Practice E739.
8.2 Geometry—In addition to the requirements described in Test Methods D5766/D5766M and D6484/D6484M, the specimen
geometry shall satisfy the following requirements:
8.2.1 Stacking Sequence—The stacking sequence should be evaluated for free edge effects to minimize the likelihood of edge
delamination initiation.
8.2.2 Specimen Configuration—The test specimen configuration shall be in accordance with Test Methods D5766/D5766M
Configuration A for tension-tension loading or D6484/D6484M for tension-compression and compression-compression loading.
8.3 Specimen Preparation—Specimens shall be prepared in accordance with Test Method D5766/D5766M or Test Method
D6484/D6484M. Spe
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